This invention relates to a meter for motorcycles or the like, and in particular to an approach to connecting the individual wires of a wire bundle to an indicator dashboard or similar meter (hereafter collectively referred to as “dashboard”) that is mounted to the motorcycle bar for displaying information (speed, temperature, etc.).
The wire bundle comprises several insulated wires that emanate from connections to detectors or sensors that are located on the vehicle away from the dashboard. The wires are bundled within a protective outer sheath. The end of the sheath enters the dashboard case and the individual wires are connected in some manner to the main circuit board of the dashboard.
FIG. 1 illustrates a prior art approach for connecting the individual wires of a wire bundle to an indicator dashboard. The case 1 of the dashboard is typically mounted in front of the motorcycle bar to enable easy viewing of the dashboard display by a rider.
A battery 6 is secured in a mounting in the case by a cover 7 and O-ring 5. The case 1 includes and interior 12 that houses the main circuit board and associated display components. FIG. 1 shows the bottom of the case housing 13 and a resilient seal 3 that fits between the housing and a case cover (not shown) that includes a transparent lens for viewing the display that is housed in the case.
A wire bundle 11 is enclosed in a protective sheath 10 and enters an opening in the back of the case 1. As shown in the exploded view of FIG. 1, the termini of these wires 11 (hereafter sometimes referred to as “entry” wires) are connected to the underside of an interface printed circuit board (PCB) 2. Near one edge of that PCB, the ends of several, smaller “internal” wires 15 are joined to the upper surface of the interface PCB 2. The internal wires 15 are bent to extend away from and generally parallel to the plane of the PCB. The outer ends of the internal wires 15 are crimped into a connector 14 that connects to the main circuit board (not shown) that is carried inside the case.
As part of the assembly process for this device, the PCB 2 is seated inside of a well 16 that is defined in the interior 12 of the case 1. The well 16 is a compartment that is defined by the back wall of the case and by four, inwardly projecting thin sidewalls 17 that define a cubical volume within which the PCB 2 is secured. The wire bundle 11 extends through the opening in the back wall of the meter case to protrude inside the well 16, for connection to the interface PCB as noted above. The well 16 is filled with epoxy for the purpose of providing strain relief and preventing water from migrating into the case.
The prior art assembly process for connecting the internal wires 15 between the upper surface of the interface PCB 2 and the main circuit board, as noted above, requires soldering of the ends of the wires 15 to the PCB and crimping the other ends of the wires into a connector that is in turn inserted into the mating connector carried on the main circuit board. To accomplish the insertion, and to facilitate handling of the wires 15 during assembly, the length of the wires between the PCB and connector 14 is made slightly longer than the distance between the wire ends at the PCB and the connector when finally assembled. Accordingly, each of the wires is necessarily bent slightly during and after assembly. Controlling the final configuration of the bends is difficult because each individual wire is free to buckle in any direction (upwardly, downwardly or sideways). Sideways buckling can be particularly troublesome because such a “stray” buckled wire can obstruct assembly or hinder connection of other components within the compact dashboard case. Thus, extra assembly time and cost is required to carefully control the buckling direction of all of the wires to avoid strays.
The prior art device is also susceptible to failure attributable to vibration and penetration of moisture into the case. In particular, the solder joints of the internal wires can be stressed by the continuous vibration occurring during operation of the motorcycle, and eventually separate from the PCB 2 at the location where the wire ends are soldered to the PCB. One way to address this problem is to reduce the mass of the wires (hence reduce the damaging energy transmitted via vibration) by using very small diameter wires. However, when wires are connected to the PCB using modern lead-free solders, the attendant higher melting points of such solders calls for relatively stiffer insulating jackets over the wire than is required with lead-based solders. The stiffer insulation in turn increases the overall mass of the wires, and thus returns the damaging vibration problem.
Finally, despite the presence of sealing epoxy in the well 16 mentioned above, some moisture may penetrate the well, and the presence of the internal wires that extend from the PCB in the well to the connector 14 on the main circuit board provide between the wires a capillary path for the moisture to flow to the connector 14 and damage the main circuit board. This capillary flow seems to be enhanced by the presence of an array of grooves 20 formed in the upper edge of the prior art sidewall 17 over which the internal wires 15 pass, each groove receiving a wire.